Biological Control of Blue Heliotrope

A report for the Rural Industries Research and Development Corporation by David Briese and Miguel Zapater

September 2001 RIRDC Publication No 01/119 RIRDC Project No CSE-82A

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© 2000 Rural Industries Research and Development Corporation. All rights reserved. ISBN 0 642 58341 2 ISSN 1440-6845 Biological Control of Blue Heliotrope Publication No. 01/119 Project No. CSE-82A The views expressed and the conclusions reached in this publication are those of the author and not necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any person who relies in whole or in part on the contents of this report. This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the Publications Manager on phone 02 6272 3186. Researcher Contact Details David Briese GPO Box 1700 Canberra ACT 2601 Phone: 02 6246 4045 Fax: 02 6246 4000 Email: David.Briese@ento.csiro.au

Miguel Zapater Facultad de Agronomía Universidad de Buenos Aires Av. San Martín, 4453 1417 Buenos Aires, Argentina Email: mmzapater@arnet.com.ar

RIRDC Contact Details Rural Industries Research and Development Corporation Level 1, AMA House 42 Macquarie Street BARTON ACT 2600 PO Box 4776 KINGSTON ACT 2604 Phone: 02 6272 4539 Fax: 02 6272 5877 Email: rirdc@rirdc.gov.au. Website: http://www.rirdc.gov.au Published in August 2001 Printed on environmentally friendly paper by Canprint

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Foreword Blue heliotrope, Heliotropium amplexicaule Vahl, is a perennial, spreading broad-leaf weed of temperate South American origin. It was introduced into Australia in the late 19th century as a garden ornamental and now occurs in four states. In northern New South Wales and southern Queensland it has undergone rapid recent spread in cultivated pastures. It is considered a serious weed in these areas because it competes with desirable summer pasture species and is toxic to stock. Conventional methods, including herbicide use have had limited success in reducing its impact and have not stopped its spread. Moreover, recent concerns raised over contamination of livestock and livestock produce by the build up of residual chemicals in the soil, emphasise the need for non-chemical, non-polluting methods of weed control. Biological control would provide such an option and enhance Australia’s reputation for exporting clean livestock produce.

This publication describes investigations in South America aimed at identifying natural enemies of blue heliotrope in its native range and determining their potential for biological control of the weed in Australia. One agent, the leaf-beetle, Deuterocampta quadrijuga, was selected for introduction and the report describes the formal quarantine testing, leading to an application for release of the beetle in the field. Finally, recommendations are made on future work needed to achieve effective biological control. This project was funded from RIRDC Core Funds, which are provided by the Federal Government, in order to ensure the successful initiation of the project. This report, a new addition to RIRDC’s diverse range of over 700 research publications, forms part of our Resilient Agricultural Systems R&D program, which aims to foster agri-industry systems that have sufficient diversity, flexibility and robustness to be resilient and respond to challenges and opportunities. Most of our publications are available for viewing, downloading or purchasing online through our website: downloads at www.rirdc.gov.au/reports/Index.htm purchases at www.rirdc.gov.au/eshop

Peter Core Managing Director Rural Industries Research and Development Corporation

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Acknowledgments This project would not have been possible without the efforts of the Blue Heliotrope Action Committee, a coalition of landholders, Landcare coordinators, State and local government representatives formed in 1996 to promote the better management of this weed. Their belief that biological control could provide a solution to the problems of blue heliotrope and their tireless lobbying of government and research agencies for support was critical to the funding of the project. Without detracting from the efforts of all members of this group, special thanks are due to Bill Lambell and Jen Finlayson for their ongoing help and interest with this project. Thanks are also due to Bill Pettit, Gerardo Serra, and Gladys Perez-Camargo for their contributions to the research in Argentina. Andrea Andorno undertook studies on the host-range of insects as part of an Agricultural Science thesis at the University of Buenos Aires. Penny Reynolds carried out the initial part of the blue heliotrope ecology studies in Australia as part of an Agricultural Science degree at Sydney University. Plants for formal host-specificity testing were supplied by: Laurie Adams, Australian National Herbarium, Canberra, ACT; Robin Coles, Adelaide, SA; Penny Edwards, CSIRO, Darwin, NT; Graeme Errington, Mt Annan Botanic Gardens, NSW; Peter Horsfall, Sturt Desert Park, NT; Tanya McAndrew and Michael Day, Queensland Department of Natural Resources and Mining, Sherwood, QLD; Chris O’Donnell, Department of Primary Industries, Gayndah, QLD; and Garry Sankowsky, Yuruga Nursery, Atherton, QLD. Andi Walker carried out the host-specificity tests in the CSIRO Black Mountain Quarantine Facility.

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Contents

Foreword iii Acknowledgments iv Executive Summary vi 1. Introduction 1.1 Background 1 1.2 Project Aims 2 2. Studies in Argentina 2.1 Blue Heliotrope Surveys 3 2.2 Preliminary Host-Specificity Testing 6 2.3 Impact of Candidate Agents 9 2.3.1 Deuterocampta quadrijuga 9 2.3.2 Longitarsus sp. 10 3. Studies in Australia 11 3.1 Ecology of Blue Heliotrope 11 3.2 Quarantine Testing of Deuterocampta quadrijuga 12

4. Discussion 16

4.1 Strategy for the biological control of blue heliotrope 16 4.2 Implications 16

5. Recommendations 17 6. References 18

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Executive Summary Blue heliotrope, Heliotropium amplexicaule Vahl, is a perennial, spreading broad-leaf weed of temperate South American origin. It was introduced into Australia in the late 19th century as a garden ornamental and now occurs in four states. In northern NSW South Wales and southern Queensland it has undergone rapid recent spread in both cultivated pastures and crops. It is considered a serious weed in these areas because it competes with desirable summer pasture species and is toxic to stock. Herbicides have had limited success in reducing its impact and have not stopped its spread. Biological control offers an important control option that could reverse the current low success in management of this weed. A research base was set up in Argentina, and a local entomologist contracted for the project. Three surveys conducted throughout the range of blue heliotrope in Argentina identified four insect species as having potential for biological control: the leaf feeding beetle, Deuterocampta quadrijuga; the flea-beetle, Longitarsus sp., which feeds on leaves as an adult and on roots as a larva; the bug, Dictyla sp., which sucks sap from the cells of leaves, killing them; and the thrips, Haplothrips heliotropica, whose feeding causes deformation of leaves and buds. In addition, a pathogen, the leaf-blotch fungus Pseudocercosporella sp., was found to cause die-back of infected blue heliotrope plants. An open-field host-specificity trial was carried out to make a preliminary assessment of the host-range of the four insect species. It showed that all four insects were restricted to the genus Heliotropium, with evidence of strong preferences for a limited number of species within that genus. The field surveys had indicated that the leaf-beetle, D. quadrijuga, and the flea-beetle, Longitarsus sp., were the most damaging agents. Field experiments were set up to study the biology and impact of these two species, and showed that both were capable of completely defoliating blue heliotrope plants. The leaf-beetle caused relatively rapid defoliation by mid-summer under natural conditions, while the flea-beetle had a slower impact, causing a gradual decline in plant size and death of most plants by autumn. The leaf-beetle was selected for the first introduction into Australia. Testing at the Black Mountain Quarantine Facility, Canberra, showed that it was restricted to South American sections of the genus Heliotropium as host-plants and did not pose a risk to non-target plant species, including native Australian Heliotropium species. Based on these results, Australian plant biosecurity authorities approved the release of D. quadrijuga for the biological control of blue heliotrope in July 2001. The work of this project will lead to the field release of the leaf-beetle, for biological control of blue heliotrope in Australia. The first such release is planned for October 2001. The project enabled the development of a biocontrol strategy, which suggests that control would be more effective if additional agents, such as a root-feeding insect or pathogen, could complement the actions of the leaf-beetle. Such agents have been identified in the current project, but further work is needed to determine if they are safe for release. Successful biological control would lead to a significant reduction in the economic and environmental impact of this toxic noxious weed through environmentally-benign and self-sustaining means. It would also provide an additional tool for the integrated management of the weed. However, to fully realise the potential for biological control, further work is needed to complete introduction of the complementary guild of agents, ensure their redistribution and monitor their impact in the field.

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1. Introduction 1.1 Background Heliotropium amplexicaule Vahl (blue heliotrope) is native to South America, occurring in northern and central Argentina, southern Bolivia, Uruguay and the extreme south of Brazil (Johnston 1928). It was introduced into Australia as an ornamental plant in the late 1800s. Over the last 40 years there has been a rapid and continuing expansion of its range and there are now widespread infestations in south-east Queensland and northern New South Wales, with scattered colonies extending into Victoria and further into South Australia (Parsons & Cuthbertson 1992). Blue heliotrope infests over 110,000 ha in New South Wales alone (Da Silva 1991) where it is a declared noxious weed in 14 local government areas. It contains pyrrolizidine alkaloids that are toxic to livestock, causing liver damage and stock death (Glover & Ketterer 1987). In agricultural systems, production losses occur due to competition by blue heliotrope with more desirable cropping and pasture species and through a decline in animal performance as a result of its toxicity. This weed is already a serious weed of pastures and can adversely affect other production systems and natural ecosystems (Newell 1997). Cultivation encourages spread by stimulation of germination and regeneration from decapitated rootstocks and plant fragments. The chemicals currently registered for blue heliotrope have had limited success and are not selective. Its continued spread and the increasing rate at which this is occurring indicates that current control methods are not successful, and Newell (1997) considers it to be on the verge of becoming a much more serious problem for agriculture in eastern Australia. A model of the actual and predicted distributions of blue heliotrope in Australia (Fig. 1) confirms the risk of more widespread infestations of the weed to Australian agriculture. Fig. 1. Predicted range of blue heliotrope in Australia, based on temperature, rainfall quantity and rainfall seasonality, using the Bioclim® climate-modelling module of the Biolink® informatics software package (the darker the shading the more suitable for blue heliotrope). White squares indicate current distribution records.

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An integrated management approach is seen as the only way to combat this weed, and an important part of such a strategy would be biological control, which would be both environmentally benign and self-perpetuating. Funding from the International Wool Secretariat enabled Wapshere (1991) to conduct two brief surveys of the weed in its South American native range in November 1990 and March 1991 to investigate the potential for biological control. He identified four insects as possible candidate control agents. Climate matching showed that the areas surveyed for blue heliotrope and its natural enemies were closely matched to the principal infested areas in Australia. Given that four damaging agents were found during the brief survey and that they should be adapted to Australian climates, Wapshere was optimistic about the chance of biological control. To achieve this, Wapshere (1991) recommended that the preliminary surveys in South America be extended to determine the full range of natural enemies on the weed, that a fuller study of the population dynamics of the weed be made in its natural range to determine the impact of the natural enemies and that the host-specificity of the four candidate agents mentioned above be determined. Biological control offers an important control option that could reverse the current situation regarding control. While no cost-benefit analyses have been carried out for blue heliotrope, data for similar pasture weeds suggest that biocontrol could provide benefits of several million dollars per year in New South Wales alone at current infestation levels. This would not include the additional benefits of preventing further increase. Biological control is an environmentally benign control method and, once in place, is self-sustaining, thereby reducing the long-term economic and environmental costs of current herbicide-oriented control methods. 1.2 Project Aims The principal aims of this project are to evaluate the potential of natural enemies from the native South American range of blue heliotrope for control of the weed, and, if suitable, to introduce of the first agent into Australia for biological control of blue heliotrope. The particular objectives needed to achieve these aims include: undertaking surveys for potential biological control agents of blue heliotrope in Argentina,

conducting studies of their host-range, biology and impact on the plant in order to prioritise

agents for introduction into Australia, introducing into quarantine in Australia and determining the safety for release of the prioritised

biological control agent, and, if deemed safe, obtaining approval for release of the agent into the field.

The project will provide information to decide whether biological control is a feasible option for the management of blue heliotrope in Australia, and how it should proceed. Any subsequent release and evaluation of agents against blue heliotrope would form a separate project.

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2. Studies in Argentina 2.1 Blue Heliotrope Surveys Blue heliotrope, H. amplexicaule, is native to South America, and the largest part of its range is across central and northern Argentina (Fig. 2). A base was therefore established at the University of Buenos Aires for surveys and experimental work on candidate biological control agents. There are 24 native species of Heliotropium in Argentina, but the composition is quite different to the native Heliotropium flora of Australia (Table 1). Therefore, in addition to surveying blue heliotrope, efforts were made to survey the natural enemies of other species of Heliotropium in Argentina. This would provide an initial idea of the host range of natural enemies collected from blue heliotrope. Fig. 2. Blue heliotrope sites surveyed (black squares) in Argentina in November 1998, February 2000 and June 2000. White squares indicate other location records. Circles indicate regions discussed in the text.

Table 1. Australian and Argentine species of Heliotropium (data from Craven (1996) and Gangui (1955)).

Sections of Heliotropium Australia Argentina Common species native exotic Chaemotropium 1 Heliotropium 5 1 Orthostachys 71 8 Platygyne 1 2 H. curassavicum Tiaridium 1 3 H. indicum Heliotrophytum 1 4 H. amplexicaule Coeloma 4 Hypsogenia 1 Plagiomeris 2

Sierra de la Ventana

Pergamino

Entre Rios

Cordoba

Tandil

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Three surveys were made; in November 1998, February 2000 and June 2000. This covered the spring, late summer and late autumn periods and included the most important regions where the weed was found, Cordoba, Pergamino, Sierra de la Ventana, Tandil and Entre Rios. The sites visited during these surveys are shown in Fig. 1. In all areas sampled, blue heliotrope was found to occur in small roadside patches. Population densities of the weed declined rapidly away from the roadside in native vegetation or pasture. New infestations of the weed were always associated with disturbance, such as grading, fire or slashing. This suggests that blue heliotrope is an early successional plant in its native range and is eventually displaced by more competitive plant species, only to re-establish again following further disturbance. This is a very different life-history to that occurring in its introduced range in Australia, where long-lived populations of the weed dominate large areas. Blue heliotrope plants were also much more variable in plant form, leaf shape and flower colour in their native range, supporting the idea that Australian infestations of the weed originate from a garden cultivar of the plant. One major difference between Australian and Argentine populations of blue heliotrope is the level of attack by natural enemies. In Australia, apart from occasional and localised defoliation by larvae of the native moth, Utethesia pulchelloides, there is virtually no insect attack. In contrast, damage by one or more species of insect or pathogen was noticed at all sampled locations of blue heliotrope in Argentina. Four species of insect and one pathogen were common either locally or throughout the distribution of blue heliotrope (Table 2) and were considered to warrant further investigation as biological control agents. Table 2. Agents with biocontrol potential collected from Heliotropium amplexicaule in Argentina during 1998-99. Agent Region Cordoba Pergamino Sierra de la

Ventana Tandil Entre

Rios Insect Coleoptera: Curculionidae Deuterocampta quadrijuga +++ 0 0 0 0 Coleoptera: Halticini Longitarsus sp. + +++ + + + Hemiptera: Tingidae Dictyla spp. ++ + +++ + + Thysanoptera: Phlaeothripidae Haplothrips heliotropica + + 0 + + Pathogen Fungi Imperfecti: Hyphomycetales Pseudocercosporella sp. 0 0 0 0 ++

0 = not found, + = rare, ++ = common, +++ = abundant

The most damaging agents on blue heliotrope were the leaf-beetle, Deuterocampta quadrijuga, and the flea-beetle, Longitarsus sp. While D. quadrijuga only occurred in one of the five regions surveyed (Table 2), massive larval and adult populations of the beetle have been recorded defoliating blue heliotrope in the past (Bruch 1940), and observations in the Cordoba region during these surveys confirmed that the beetles were capable of completely defoliating blue heliotrope plants (see sections 2.3). Adults of the flea-beetle, Longitarsus sp. were also found feeding on leaves, but, as their larvae normally feed on root tissue, they are of interest for biological control. Observations at the Pergamino site, where the flea-beetle is most common, suggest that they can cause plant death (see section 2.3). The cell-sucking bugs, Dictyla sp., whose feeding caused leaf chlorosis and death, seemed to be the most widespread agent (Table 2), and were occasionally found to cause severe damage to blue heliotrope. The other agent of interest is a species of thrips, Haplothrips

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heliotropica, which fed on growing points causing stunting and deformation of leaves and shoots, though it did not appear able to kill plants. These agents appear to be associated with plant species of the Heliotropium section Heliotrophytum. In addition to blue heliotrope, H. amplexicaule, all four species were found to attack H. nicotianaefolium, while Haplothrips and Dictyla also attacked H. phylicoides, both of which belong to Heliotrophytum. However, none of the species from other sections of Heliotropium, such as H. curassavicum, H. mendocinum and H. veronicifolium, were observed to be attacked by these four insect species.

Fig. 3. Candidate biological control agents for blue heliotrope (black bar = 1 mm). The most damaging agents on blue heliotrope were the defoliating beetle, Deuterocampta quadrijuga, and the cell-sucking bugs, Dictyla spp. Dictyla spp., whose feeding caused leaf chlorosis

Longitarsus sp. - adults of this flea-beetle feed on leaf tissue and larvae are thought to feed on the roots.

Deuterocampta quadrijuga – both adults and larvae of this leaf beetle can

Dictyla sp. – adults and nymphs of this hemipteran

bug suck leaf cells.

Haplothrips heliotropica - feeding by

adults and nymphs of this thrips causes leaf and bud deformation.

Pseudocercosporella sp. – this fungus forms dark blotches on the leaf surface surrounded by chlorotic

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and death, seem to be the most widespread agent (Table 2), while D. quadrijuga only occurred in one of the five regions surveyed (Table 2). However, massive larval and adult populations of the beetle have been recorded defoliating blue heliotrope in the past (Bruch 1940), and observations in the Cordoba region during these surveys confirmed that the beetles were capable of completely defoliating blue heliotrope plants (see sections 2.3). In fact, populations of the target weed declined severely in autumn in areas where they were abundant. Adults of the flea-beetle, Longitarsus sp. were found more rarely feeding on leaves, but, as their larvae normally feed on root tissue, they are of interest for biological control. Observations at the Pergamino site, where the flea-beetle is most common, suggest that they can cause plant death (see section 2.3). The other agent of interest is a species of thrips, Haplothrips heliotropica, which fed on growing points causing stunting and deformation of leaves and shoots, though it did not appear able to kill plants. These agents appear to be associated with plant species of the Heliotropium section Heliotrophytum. In addition to blue heliotrope, H. amplexicaule, all four species were found to attack H. nicotianaefolium, while Haplothrips and Dictyla also attacked H. phylicoides, both of which belong to Heliotrophytum. However, none of the species from other sections of Heliotropium, such as H. curassavicum, H. mendocinum and H. veronicifolia, were observed to be attacked by these four insect species. An examination of Herbarium records for blue heliotrope at the International Mycological Institute revealed that a Phloeospora sp. from the Entre Rios region of Argentina, had been deposited in 1990. The specimen (IMI 344100) comprises a number of shoots heavily colonised and damaged by circular, greyish-black necrotic lesions. This area was resurveyed in June 2000, in the company of Dr L. Morin, a plant pathologist, and populations of blue heliotrope infected with the pathogen were located and sampled. The pathogen was isolated and correctly identified as Pseudocercosporella sp. An isolate of the pathogen was imported into the Black Mountain Quarantine Facility in Canberra, Australia, where it is currently being cultured for evaluation as a biological control agent. 2.2 Preliminary Host-Specificity Testing Preliminary host-specificity testing of the four candidate insect agents, D. quadrijuga, Longitarsus sp., Dictyla sp. and H. heliotropica, was carried out in the open field in Argentina, as part of a graduate thesis (see Andorno 2001). The target plant, H. amplexicaule, and six non-target species, of varying phylogenetic relatedness, were planted out in a random block design in a field at the Agronomy Faculty of the University of Buenos Aires, in an area where H. amplexicaule did not occur naturally (Fig. 4). Three blocks of plants were used. Adults of Longitarsus sp. were released into the first block, adults of Dictyla sp. and H. heliotropica into the second plot and adults of D. quadrijuga into the third plot. The experiment was carried out in two phases, designed to measure host-choice behaviour both in the presence and absence of the target weed. The first phase of the test allowed the insects to choose between target and non-target plants. Following the release of adult insects of each species into the plots on February 4, their subsequent position and feeding, numbers of eggs laid and larvae developing were recorded at 1-3 day intervals for a period of 3 months until May 11. In the case of D. quadrijuga, H. heliotropica and Dictyla sp. when given a choice, no attack occurred on the Heliotropium species from a different section, or on two species from related genera in the family Boraginaceae, nor on two more distantly related species of the order Lamiidae. Only the two species of Heliotropium belonging to the section Heliotrophytum (H. amplexicaule and H. nicotianaefolium) were fed on and oviposited on by adults, or fed on by the emerging larvae (Fig. 5). This indicates a high degree of specificity. Longitarsus sp. showed a strong preference for these two species initially, but as feeding damage became more severe on H. amplexicaule and H. nicotianaefolium, adult flea-beetles commenced feeding on H. arborescens, the third species of Heliotropium (Fig. 6). This suggests that it might have a slightly broader host-range, albeit still restricted to the genus Heliotropium.

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Fig. 4. Example of random block layout of test plants in the field plot at the University of Buenos Aires

A1 Heliotropium amplexicaule

A2 Lavandula dentata

A3 Symphytum asperum

A4 Myosotis sp.

A5 Heliotropium nicotianaefolium

A6 Heliotropium arborescens

B1 Oreganum vulgare

B2 Heliotropium arborescens

B3 Heliotropium amplexicaule

B4 Lavandula dentata

B5 Symphytum asperum

B6 Myosotis sp.

C1 Symphytum asperum

C2 Myosotis sp.

C3 Oreganum vulgare

C4 Heliotropium arborescens

C5 Heliotropium amplexicaule

C6 Lavandula dentata

D1 Heliotropium arborescens

D2 Heliotropium amplexicaule

D3 Lavandula dentata

D4 Symphytum asperum

D5 Myosotis sp.

D6 Oreganum vulgare

E1 Myosotis sp.

E2 Oreganum vulgare

E3 Heliotropium arborescens

E4 Heliotropium amplexicaule

E5 Lavandula dentata

E6 Symphytum asperum

F1 Lavandula dentata

F2 Symphytum asperum

F3 Myosotis sp.

F4 Oreganum vulgare

F5 Heliotropium arborescens

F6 Heliotropium amplexicaule

Fig. 5. Host-specificity of Deuterocampta quadrijuga in an open-field plot in Argentina. Data indicate the mean damage rating at the end of the period when there was a choice between H. amplexicaule and non-target plants.

Open-field host choice test

0 1 2 3 4

H. amplexicaule

H. nicotinaefolium

H. arborescens

Myosotis sp.

Symphytum asperum

Lavandula dentata

Origanum vulgare

Mean damage per plant (0 = none, 4 = maximum)

Deuterocampta

Longitarsus

Dictyla

Haplothrips

Lam

iidae

Bora

gina

ceae

Hel

iotro

pium

Hel

iotro

phyt

um

Ord

erFa

mily

Gen

usS

ectio

n

In the second no-choice phase of the test, the two host plant species were cut and left on the plot, to force natural dispersal of the agents amongst the remaining non-target plants. When these host-plant were removed, neither H. heliotropica nor Dictyla sp. were found in the plots again and there was no damage to the remaining non-target plants (Fig. 6). A few D. quadrijuga adults were found on the H. arborescens for up to 14 days after removal of their host plants, and there was evidence of

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exploratory feeding (Fig. 6) but no oviposition. The insects subsequently left these plants, and no D. quadrijuga were found on other Boraginaceae (Myosotis sp. and Symphytum asperum) or Lamiidae (Lavandula dentata and Oreganum vulgare) test plants. This indicates that they either died in the case of larvae, or dispersed further in the search of a favoured host in the case of adults. In the absence of their preferred Heliotropium hosts, Longitarsus sp. adult concentrated on H. arborescens and damage to that species increased substantially. However, no species outside the genus Heliotropium were attacked. Fig. 6. Change in damage rating to species before (choice phase) and after (no-choice phase) the primary host species, H. amplexicaule and H. nicotianaefolium, were cut from the plot. No species other than those indicated were attacked.

Deuterocampta

0

1

2

3

4

4/02 18/02 3/03 17/03 31/03 14/04 28/04 12/05Date

Dam

age

ratin

g

H. amplexicaule

H. nicotianaefolium

H. arborescensCUT

Longitarsus

0

1

2

3

4

4/02 18/02 3/03 17/03 31/03 14/04 28/04 12/05Date

Dam

age

ratin

g

CUT

Dictyla

0

1

2

3

4

4/02 18/02 3/03 17/03 31/03 14/04 28/04 12/05Date

Dam

age

ratin

g

CUT

Haplothrips

0

1

2

3

4

4/02 18/02 3/03 17/03 31/03 14/04 28/04 12/05Date

Dam

age

ratin

g

CUT

The results suggested that all four species were restricted to the genus Heliotropium and show differing degrees of discrimination within that genus; the thrips, H. heliotropica, seems the most restricted, with a strong preference for H. amplexicaule; the sap-sucking bug, Dictyla sp. showed equal preference for H. amplexicaule and H. nicotianaefolium and did not attack any other species in their absence; the leaf-beetle, D. quadrijuga, showed a similar response to these two species, but did some exploratory feeding on the other species of Heliotropium when these primary hosts were removed; and the flea-beetle, Longitarsus sp., fed on the other Heliotropium species, initially not at all, to a small extent after the primary hosts became damage, but extensively when they were removed. 2.3 Impact of Candidate Agents 2.3.1 Deuterocampta quadrijuga

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An experiment was set up in November 1999 to measure the impact of the leaf-beetle, D. quadrijuga, on blue heliotrope, under natural levels of attack. Three sites were selected in the Cordoba region of central Argentina and paired blue heliotrope plants were marked at each site. One pair was treated regularly with a granular insecticide to prevent insect damage and the other left untreated. At 2-3 week intervals, the plants were inspected and measurements of plant growth and flowering made. The numbers of eggs, larvae and adult D. quadrijuga were also counted and an estimate of feeding damage made. Results from these field studies indicated that there was a rapid increase in D. quadrijuga population size during spring, with a subsequent rapid reduction in plant size (Fig. 7). Feeding by adult and larval D. quadrijuga on blue heliotrope leaf and stem tissue had completely removed the above ground biomass of H. amplexicaule plants before mid-summer (Fig. 7). At this stage adult beetles were observed to move on to other blue heliotrope plants in the vicinity that still had foliage. Although defoliated plants eventually recovered from rootstocks in autumn, and although there was no subsequent attack by the leaf-beetle, their size remained greatly reduced (Fig. 7). D. quadrijuga females live for up to four months and may lay up to 1400 eggs during that period. Hence they have the capability of very rapid increase and multiple generations over a field season. It seems likely that, at high levels of beetle population where all plants in an infestation are attacked at the same time, any such regrowth would be eaten by later generations of the beetle. Under Australian conditions, such reduction of above ground biomass would lower the risk of stock poisoning and decrease the competitiveness of the plant with desirable pasture species. Fig. 7. Changes over time in feeding damage by the leaf-beetle, Deuterocampta quadrijuga, on blue heliotrope, and the resultant reduction in plant size.

Impact of Deuterocampta on H. amplexicaule

0

1

2

3

4

9/11 23/11

7/12 21/12

4/1 18/1 1/2 15/2 29/2 14/3 28/3 11/4 25/4 9/5

Date

0

10

20

30

40

50

Mea

n pl

ant d

iam

eter

(cm

)

Deuterocampta damage

Plant size

Mea

n da

mag

e pe

r pla

nt

(0 =

non

e, 4

= m

axim

um)

2.3.2 Longitarsus sp. Similar field studies were set up at Pergamino, near Buenos Aires, in November 1999 to measure the impact of a naturally-occurring population of the flea-beetle, Longitarsus sp. Adults of this beetle

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chewed small holes into the leaves, and necrotic lesions originating from these destroyed the remaining leaf tissue. Importantly, the larvae of this beetle are believed to feed on the roots of the plant, which would greatly increase their value as biological control agents. Three sites were set up and monitored similarly to those described above for Cordoba. Unfortunately, attempts to measure oviposition and study larval feeding were unsuccessful, but the overall effect of feeding damage by Longitarsus sp. was measurable. Compared to D. quadrijuga, there was a slower increase in plant damage, reaching maximum impact by the beginning of autumn (Fig. 8). Blue heliotrope plant continued to grow during the early stages of attack, but from mid-summer there was a gradual decline in plant condition and size until late autumn (Fig. 8). Unlike the study of the leaf-beetle, where all plants survived defoliation, Longitarsus sp had killed several of the plants at the end of this period. It is suspected that larval feeding damage to the roots might be a prime cause for this different response to herbivore damage, but further studies are needed to confirm their role in the observed impact on the target weed. Fig. 8. Changes over time in feeding damage by the flea-beetle, Longitarsus sp., on blue heliotrope, and the resultant reduction in plant size.

Impact of Longitarsus on H. amplexicaule

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3. Studies in Australia 3.1 Ecology of Blue Heliotrope There has only been only one study of the ecology of blue heliotrope in Australia, by Da Silva (1991). This provided valuable information on the life-cycle of the plant, reproductive biology and seed germination requirements, but did not examine the population structure and dynamics and soil seed bank in the field. It was considered essential to obtain baseline information on these aspects of blue heliotrope ecology, in order to evaluate the subsequent impact of biological control agents. An agreement was made with the Agricultural Science Department of Sydney University to conduct these baseline studies as part of an undergraduate thesis (see Reynolds 2000). Three study plots were selected; two on a property “Weenya” near Gulargambone, NSW (31°16´S x 148°48´E), and one in the Warrumbungles National Park (31°17´S x 149°01´E). Measurements of plant density, growth and seed production were collected at 3-4 week intervals from March to September 2000, and data collection is continuing following the completion of the thesis. Over a 12-month period, the mean density varied at the three sites from 2-4 plants per m2 at the new Weenya infestation, 15-27 plants per m2 at the older Weenya infestation and 6-10 plants per m2 at the National Park site (Fig. 9). The decline in density over winter was due to die back of above ground shoots and subsequent recovery from perenniating rootstocks (Fig. 9). No significant germination and establishment of seedlings occurred during the 12-month period and the population remained relatively stable. Three flushes of flowering and seed production were observed between early spring, when plants produced new growth and autumn when above ground growth commenced to die off. Using a relationship between flower number and cyme length, seed production at the Warrumbungles National Park site during 2000/01 was estimated to be 18600 ± 4800 seeds per m2, of which 76% was produced in the spring flowering flush, 16% in the early-summer flush and 8% in the late-summer flush. Fig. 9. Change in density of blue heliotrope plants at three study sites in central NSW (bars indicate standard errors).

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In August 2000, soil cores were taken from five sites with differing histories of blue heliotrope infestation in order to study the dynamics of the soil seed reserve. These sites included the two plots at “Weenya”, one of which was known to be three or less years old (i.e. one season of seed production) and the other up to eight years old, the plot within the Warrumbungles National Park, which has been heavily infested for over 15 years. These three sites provided an indication of soil seed build up. The remaining two sites were kangaroo exclosures within the park. These sites were set up to determine the effect of preventing kangaroo grazing of palatable plant species on weed management (Moss 1997). Such exclusion led to rapid competitive replacement of dense blue heliotrope by other plant species, which meant that there had been no input into the existing soil seed reserves for two years and 12 years, respectively. This provided an indication of the decline in seed reserves that might be occur following successful biological control (Fig. 10). Fig. 10. Probable pattern of soil seed reserve build up following infestation by blue heliotrope, and decline following eradication of the weed or prevention of seed production. Points indicate soil seed densities from five sites with differing histories of infestation (see text for details).

0

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Seed input No seed input seed bank increase seed bank decline

The data show that seed banks can rapidly build-up if blue heliotrope infestations are allowed to persist. The stable level, where input equals losses seems to be of the order of 50,000 seed per m2. In the absence of further seed input, this declined to 1,500 seeds per m2 over a 10- to 12-year period. Clearly, for biological control to be successful in the long-term, agents will need to significantly reduce seed input, as seed production in any one season could rapidly replenish the soil seed reserve. Site 2 at Weenya and the Warrumbungles National Park site were selected for the first release of the leaf-beetle, D. quadrijuga, should Australian plant biosecurity authorities give authorisation. 3.2 Quarantine Testing of Deuterocampta quadrijuga In January 2000, approval was given by AQIS and Environment Australia to import the leaf-feeding chrysomelid beetle, Deuterocampta quadrijuga, into the CSIRO Black Mountain Quarantine Facility, Canberra, for detailed host specificity testing. Test plants were selected on the basis of their phylogenetic relationship to the target weed, following Wapshere (1974), and representatives of the 75 species of Heliotropium that occur in Australia were chosen on the basis of geographic overlap and ecological similarity to the target weed, based on the information of Craven (1996). No-choice

13

tests, in which D. quadrijuga was exposed only to the test plant, were initially used to test both larval feeding and survival, and adult feeding and oviposition. Where no-choice tests indicated that there may be some risk, more realistic choice tests, in which D. quadrijuga was presented with a choice between target and non-target plants, were carried out to clarify the beetle’s behaviour. All tests were carried out on potted plants in mesh cages within the quarantine building. The results of the no-choice tests carried out in quarantine are summarised in Table 3. Apart from the target weed, only three other species supported larval development to adulthood; H. indicum, another introduced species of South American origin, Tournefortia sarmentosa, a member of the same subfamily Heliotropioides, and Myosotis discolor, an introduced member of the Boraginaceae. Survival rates for the congeneric H. indicum were 25% of that for H. amplexicaule, while only one adult emerged in one of the six replicates for the latter two species. In both cases, larval development was also much slower than on H. amplexicaule, indicating their poor host qualities. In the case of M. discolor, the single emerging adult had developed as a larva on juvenile leaves of seedling M. discolor. No larvae survived on more mature plants with older leaves. Larvae actually fed on many more species (23 out of 40), but in most cases this was restricted to exploratory nibbling. Larvae developed beyond the first instar only on the target weed, six other species of Heliotropium (H. arborescens, H. curassavicum, H. indicum, H. europaeum and H. supinum, all of which are either of South American or European origin, and the Australian species, H. pleiopterum), T. sarmentosa and M. discolor. The remaining Australian indigenous Heliotropium species were either not fed on at all, or only subject to exploratory nibbling, with all larvae dying before their first moult. Under no-choice conditions, adult feeding was even more restricted than that shown by larvae placed on the plants, with only 11 test species fed on. Feeding was non-existent on plant species from non-Boraginaceae families, restricted to exploratory nibbling on some Boraginaceae and slighter higher on some congeneric species. Only one species, H. indicum, which is also of South American origin, was fed on substantially (Table 3). Oviposition was broader with eggs laid on 17 of the 39 test plants (Table 3). However, in most cases, only a few eggs were laid on individual test plants and the mean numbers (fewer than 2 eggs / plant) were less than that laid on cage materials. When the target weed was presented during pre- and post-test controls, many more eggs were laid overall (mean = 39 eggs / plant) and no eggs were laid on the cage. This indicates that female D. quadrijuga lay many fewer eggs in the absence of H. amplexicaule, and those that are laid are deposited on any available substrate, including in this case cage materials or other test plants. Eggs continually develop in the ovaries of female D. quadrijuga when they receive adequate nutrition. Hence, eggs laid during the test period would have developed earlier during the pre-test controls, and females with full ovaries may have laid some eggs even in the absence of appropriate stimuli from a host-plant to oviposit. The inability of females to feed on test plants, apart from H. indicum, means that egg production, as well as oviposition, would soon cease. Choice-tests of adult feeding and oviposition, for those species that indicated some risk under no-choice tests, were even more conclusive (Table 4). The only non-target plant fed on by adults when given a choice was H. indicum, though at a much lower level than H. amplexicaule. The suitability of this plant to support the life-cycle of D. quadrijuga was also reflected in the fact that eggs were again laid on this species under choice conditions. Adults neither fed on other species tested under choice conditions nor had eggs laid on them when H. amplexicaule plants were present (Table 4). The mean number of eggs laid per H. amplexicaule plant during these tests was 33. There are two levels of risk associated with the release of an exotic biological control agent into the Australian environment; that of colonisation of non-target plants, with possible widespread, long-term population consequences and irreversible evolutionary consequences for the attacked plant, and that of collateral damage to non-target plants if the agent feeds on them any a particular stage without completing its life-cycle, which might engender localised, short-term consequences.

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Table 3. Results of no-choice host specificity testing of Deuterocampta quadrijuga. Larval survival is the absolute proportion of larvae surviving to adulthood. All other results are relative to those on Heliotropium amplexicaule.

a = Heliotropium belongs to the subfamily Heliotropioides. Different sections of the genus are indicated. b = native range of Heliotropium species c = trace indicates a score of much less than 0.01, nt = not tested due to death of plants in quarantine

Test Category Test Species OriginLarval

survivalLarval

feeding cAdult

feeding c OvipositionTarget species a

Heliotrophytum Heliotropium amplexicaule South America 0.68 1 1 1

Tiaridium Heliotropium indicum South America 0.17 0.5 0.5 0.078Heliothamnus Heliotropium arborescens South America 0 0.15 0.02 0.039Platygyne Heliotropium curassavicum South America 0 0.08 0.05 0.029Chaemotropium Heliotropium supinum Europe 0 0.08 0.04 0.015Heliotropium Heliotropium europaeum Europe 0 0.17 0 0.005Pterotropium Heliotropium asperrimum Australia 0 0.02 0 0Pterotropium Heliotropium ammophilum Australia 0 0.02 0 0Pterotropium Heliotropium pleiopterum Australia 0 0.12 0.01 0Orthostachys Heliotropium ovalifolium Australia 0 trace 0 0Orthostachys Heliotropium pachyphyllum Australia 0 0.02 0 0Orthostachys Heliotropium brachygyne Australia 0 trace 0 0Orthostachys Heliotropium tenuifolium Australia 0 trace 0 0Orthostachys Heliotropium ventricosum Australia 0 0 nt nt

Heliotropioides Argusia argentea 0 0.02 0.01 0Heliotropioides Tournefortia sarmentosa 0.02 0.12 0.02 0Boraginoides Borago officinialis 0 0 trace 0.006Boraginoides Cynoglossum australe 0 0.08 0 0.005Boraginoides Echium plantagineum 0 0 0 0Boraginoides Myosotis discolor 0.02 0.12 trace 0.004Boraginoides Myosotis exarrhena 0 0.03 0 0Boraginoides Symphytum officianale 0 0 trace 0Boraginoides Trichodesma zeylandicum 0 0 0 0.01Cordioides Cordia dichotoma 0 0 0 0Ehretoides Ehretia saligna 0 0.02 0.01 0.008Ehretoides Halgania stricta 0 0 0 0.002

Hydrophyllaceae Phacelia tanecetifolia 0 0 0 0Convolvulaceae Ipomoea muelleri 0 0 0 0.02Gentianaceae Chionogentias diemensis 0 0 0 0Lamiaceae Mentha spicata 0 0 0 0.016Solanaceae Solanum auriculare 0 0 0 0.006Verbenaceae Verbena bonariensis 0 0 0 0.001

Convolvulaceae Ipomoea batata 0 0.01 0 0Lamiaceae Lavandula sp. 0 trace 0 0Lamiaceae Oreganum vulgare 0 0 0 0Lamiaceae Thymus vulgaris 0 0 0 0Solanaceae Capsicum annuum 0 trace 0 0Solanaceae Lycopersicum esculentum 0 0 0 0Solanaceae Solanum melongena 0 0.01 0 0.009Solanaceae Solanum tuberosum 0 0 0 0Verbeniaceae Verbena citriodora 0 trace 0 0.001

Congeneric species b

Species from other genera and subfamilies within the Boraginaceae

Species from other families related to Boraginaceae

Economic species required by AQIS

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Table 4. Results of choice host specificity testing of adult Deuterocampta quadrijuga. All values are the means of results relative to those on Heliotropium amplexicaule.

Test Category Test Species Origin Adult

feeding Oviposition Target species Heliotrophytum Heliotropium amplexicaule South America 1.00 1.00 Congeneric species Tiaridium Heliotropium indicum South America 0.17 0.06 Heliothamnus Heliotropium arborescens South America 0 0 Platygyne Heliotropium curassavicum South America 0 0 Chaemotropium Heliotropium supinum Europe 0 0 Heliotropium Heliotropium europaeum Europe 0 0 Pterotropium Heliotropium asperrimum Australia 0 0 Pterotropium Heliotropium pleiopterum Australia 0 0 Orthostachys Heliotropium ovalifolium Australia 0 0 Species from other genera and subfamilies within the Boraginaceae Heliotropioides Tournefortia sarmentosa 0 0 Boraginoides Cynoglossum australe 0 0 Boraginoides Myosotis discolor 0 0 Boraginoides Trichodesma zeylandicum 0 0 Ehretoides Ehretia saligna 0 0

Field observations in Argentina, indicated that the only Heliotropium species that serve as natural hosts to D. quadrijuga belong to the South American section Heliotrophytum (see section 2.1). Open-field tests conducted at the University of Buenos Aires, confirmed this under natural conditions (See section 2.2). Under quarantine testing in Australia the only non-target species for which both adult feeding and oviposition and subsequent larval development to adulthood was recorded was H. indicum. This is also an exotic species of South American origin belonging to the section Tiaridium, which according to Foerther (1998) is closely related to section Heliotrophytum. None of the Australian species of Heliotropium, which belong to the Pterotropium and Orthostachys sections of the genus, more distantly related to South American sections (Foerther 1998), supported larval development or attracted adult oviposition above background levels. Therefore, with regard to the risk of colonisation, the results of the quarantine testing indicate clearly that the life-cycle of D. quadrijuga can be completed only on the target weed, H. amplexicaule, and the closely related H. indicum, which is itself an exotic weed in Australia (Auld & Medd 1987). Attack on this species could be considered a bonus to the current project, though the data suggest that it is a poor host relative to H. amplexicaule and it has a more tropical distribution, making such an event unlikely. With regard to possible collateral damage, minor feeding by both adults and larvae was observed on a number of test plants other than H. amplexicaule and H. indicum under no-choice conditions. The adults, which are much more mobile, were more selective in the plant species fed on under no-choice conditions and fed only on H. amplexicaule under choice conditions. Overall, this indicates that there may be, at most, a very small risk of minor exploratory feeding damage to a limited number of plant species closely related to H. amplexicaule in a situation where the target weed was completely consumed by large numbers of D. quadrijuga, creating a food shortage. Such damage would be highly localised and would have no long-term effects, as the open-field experiments in Argentina indicate that larvae would not survive on these plants and adults would disperse from them in search of H. amplexicaule under natural conditions. It is clear from the data presented here that D. quadrijuga has a highly restricted host-range and is safe to release in the field in Australia. Permission for its release as a biological control of blue heliotrope was therefore sought from Plant Biosecurity (Agriculture, Fisheries, Forests – Australia), and from Environment Australia. Approval was given in July 2001.

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4. Discussion 4.1 Strategy for the biological control of blue heliotrope Blue heliotrope is a perennial plant with a deep root system. The plant produces new shoot and leaf growth from Spring to Autumn, and can flower several times during this period. In the present study three-quarters of flowering and seed production occurred in the first flush, which finished by late spring. Seed enters a relatively long-lived seed bank. Blue heliotrope either reproduces from this seed bank or vegetatively from root buds. In winter the foliage of the plant partially dies back or is killed by frost, to regenerate the following Spring from the rootstock. The main problems caused by the weed are an ability to smother desirable summer-growing pasture species and toxicity to livestock due to the presence of pyrrolizidine alkaloids. Biological control may therefore have a number of aims. Firstly, any reduction in above-ground biomass will reduce the toxicity problem and reduce photosynthetic capability, which should render the plant less competitive with other pasture species. It would also be desirable to reduce the production of seed by blue heliotrope and drive down the size of the soil seed reserves. This should lead to an eventual decline in local blue heliotrope infestation densities and reduce the spread of the weed into new areas. Finally, any direct damage to the root system would interfere with nutrient uptake from the soil and reduce the capacity of the plant to store these nutrients in the rootstock. In its native range in Argentina, blue heliotrope is a coloniser of recently disturbed areas, but populations do not persist in many cases or remain at low levels with individual plants being much shorter-lived than in Australia. This appears to be in part due to the inability of blue heliotrope to compete with later-colonising vegetation, but also due to continued levels of natural enemy attack, which reduces its competitiveness even more. As a result of the studies reported here, two insects, the leaf-beetle, D. quadrijuga, and the root-feeding flea-beetle, Longitarsus sp., were prioritised for the biological control of H. amplexicaule in Australia. D. quadrijuga has the potential to build up population levels rapidly and can rapidly and completely defoliate blue heliotrope plants. The strategy is to have a two-pronged attack on the target weed; on the above ground biomass (photosynthetic tissue), primarily by the leaf beetle with added pressure from the adult flea-beetles, and on the below ground biomass (root reserves) by the larvae of the flea-beetle. This complementary action should increase the chances of successful biological control of this toxic weed. An agent that causes chronic lower level damage, such as the leaf-blotch fungus Pseudocercosporella sp., could also reduce the competitiveness of blue heliotrope and warrants investigation as a third prong in this strategy. 4.2 Implications Successful biological control of blue heliotrope would lead to a significant reduction in the economic and environmental impact of this toxic noxious weed through environmentally-benign and self-sustaining means. At the moment, the distribution of blue heliotrope is expanding in Australia. Biological control would reduce the capacity of the weed to disperse and prevent it from invading new areas. It would also provide an additional tool for the integrated management of the weed. However, to fully realise the potential for biological control, further work is needed to complete the complementary guild of agents, ensure their redistribution and monitor their impact in the field.

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5. Recommendations The work carried out in this project has led to the successful completion of a first phase in the implementation of biological control against blue heliotrope in Australia. Potential control agents have been assessed and a biological control strategy developed. Research has reached the stage where one agent, the leaf-beetle D. quadrijuga, has been cleared for field release in Australia. However, further funding is needed for the next phase of work in order to capitalise on the results obtained here and to ensure that biological control of blue heliotrope is achieved with minimum delay. The recommendations for this next phase are: The leaf-beetle, D. quadrijuga, should be mass-reared for release in Spring 2001

Detailed monitoring and evaluation of agent impact should be undertaken at initial release sites

Once D. quadrijuga has become established, release networks need to be developed to redistribute

the leaf-beetle throughout infested areas of New South Wales and southern Queensland and monitor its progress

Further studies should be undertaken on the flea-beetle, Longitarsus sp., in particular to evaluate the feeding activity of larvae on the root system of blue heliotrope and to determine its host-range

Further studies should be undertaken to determine the life-cycle, virulence and host-specificity of the leaf-blotch fungus, Pseudocercosporella sp., to determine its usefulness for biological control

One or both of these agents should be released and redistributed, if proven safe, to provide a complementary agent guild that attacks different stages of the blue heliotrope life-cycle.

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6. References Andorno, A. 2001. Pruebas de especificidad a campo de cuatro insectos para el biocontrol de Heliotropium amplexicaule (Boraginacea). Ing. Agric. Thesis, Agronomy Faculty, University of Buenos Aires. Auld, B.A. and Medd, R.W. 1987. “Weeds: An illustrated botanical guide to the weeds of Australia”, 256 pp Inkata Press, Melbourne. Briese D.T., McLaren D.A., Pettit W., Zapater M., Anderson F., Delhey R. and Distel, R. 2000. New biological control projects against weeds of South American origin in Australia: Blue heliotrope and serrated tussock. In “Proceedings of the 10th Symposium on the Biological Control of Weeds, Bozeman, July 1999” (N.R. Spencer, Ed.), 5-9 July 1999, pp 215-223, Montana State University, Bozeman. Bruch, C. 1940. Metamorfosis de Deuterocampta quadrijuga Stal. Misc. Entomol. 4, 200-206. Craven, L. 1996. A taxonomic revision of Heliotropium (Boraginaceae) in Australia. Aust. Syst. Bot. 9, 521-657. Da Silva, E. 1991. The ecology and control of blue heliotrope (Heliotropium amplexicaule Vahl). Final Report to the Wool Research and Development Corporation, 33 pp. Foerther, H. 1998. Die infragenerische Gliederung de Gattung Heliotropium L. und ihre Stellung innerhalb der subfam. Heliotropioideae (Schrad.) Arn. (Boraginaceae). Sendtera 5, 35-154. Gangui, N. 1955. Las especies silvestres de Heliotropium de la República Argentina. Trabaj. Mus. Bot. Univ. Nac. Cordoba 11, 481-557. Glover, P.E., and P.J. Ketterer. 1987. Blue heliotrope kills cattle. Qld. Agric. J. 113, 109-110. Johnston, I.M. 1928. Studies in the Boraginaceae - VII. 1. The South American species of Heliotropium. Contr. Gray Herb. Harv. Univ. 81, 3-83. Moss, G. 1997. Implementation of an electrified exclosure in Warrumbungles National Park: A BACI investigation of changes in vegetation dynamics and macropod population dynamics. In “Abstracts of the 9th Meeting of the Australasian Wildlife Management Society”. Newell, D. 1997. Beating blue heliotrope; solutions for long-term control, pp. 87-92. In Proceedings, 9th Biennial Noxious Weeds Conference, 16-19 September, 1997, Dubbo, NSW Agriculture, Goulburn, Australia. Parsons, W.T. and Cuthbertson, E.G. 1992. “Noxious Weeds of Australia”. Inkata Press, Melbourne, Australia. Reynolds, P. 2000. The ecology of blue heliotrope. B. Ag. Sc. Thesis, Sydney University, 67 pp. Wapshere, A.J. 1974. A strategy for evaluating the safety of organisms for biological weed control. Ann. appl. Biol. 77, 20-211. Wapshere, A.J. 1991. Report on a preliminary survey in Argentina for potential agents for the weed Heliotropium amplexicaule. Final Report to the Wool Research and Development Corporation, 10 pp. Wapshere, A.J. 1993. Climate matching and the prospects for biological control of weeds: the contrasting examples of agents for Solanum elaegnifolium and Heliotropium amplexicaule, pp 198-200. In “Pest Control and Sustainable Agriculture” (S.A.Corey, D.J.Dall and W.M.Milne, Eds), CSIRO, Melbourne.